1. Field of Invention
This invention relates to tomography and, more particularly, to three-dimensional, ultrasound tomographic mammography.
2. Description of Related Art
One approach to ultrasound breast tomography has been to have the female subject lie in the prone position in a special bed and suspend one of her breasts into a container filled with acoustical coupling fluid. Ultrasonic transducers are arranged to rotate about the suspended breast in the fluid-filled container. Transmission or reflection projections are measured and used to reconstruct tomographic images.
The rotation of the ultrasonic transducers around the breast can cause currents in the fluid and, in turn, movement of the breast during the scanning process. This can distort the tomographic images.
One effort at dealing with this problem is set forth in a U.S. Pat. No. 4,105,018, issued on Aug. 8, 1978. FIG. 3 of this patent illustrates a stationary pedestal on which the lowest portion of the breast is rested. Unfortunately, the use of such a pedestal can complicate the mechanics and process by requiring a height adjustment mechanism and associated process to accommodate breasts of different sizes. Also, it may not prevent the turbulence in the fluid from causing upper portions of the breast to vibrate during the scanning process.
Another approach is to surround the breast with a stationary foil, as shown in FIG. 7 of U.S. Pat. No. 4,485,819, issued on Dec. 4, 1984. Unfortunately, this approach may interfere with the ultrasound signals and can restrict the ability of the system to scan portions of the breast close to the chest.